P7 Page 4 Flashcards
What changes about a wave if the speed decreases?
The wavelength decreases because the frequency is always the same.
What is the speed of a wave affected by?
Density of the substance/medium it is travelling in.
Explain how refraction occurs.
If a wave meets a different medium at an angle part of the wave hits the boundary first and slows down while another part carries on at the first, faster speed for a while. So the wave changes direction.x
Explain how a converging lens focus’s light waves to form an image of the object.
As the light rays hit the surface of the lens and passes from air to a glassy, it slows down. This causes the light ray to bend towards the ‘normal’. When it his the ‘glass to air’ boundary on the other side it speeds up and bends away from the normal.
Explain how a triangular prism can refract light to form a spectrum.
A rectangular prism has parallel boundaries, so the rays bend one way as they enter, and then bend back again by the same amount as they leave.
But with a triangular prism, the boundaries aren’t parallel, which means the different wavelengths don’t combine and you get a spectrum.
Why do wavelengths spread out when refracted?
Different wavelengths refract by different amounts. So white light(all the lights combined) disperses into its different colours as it enters the prism.
